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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ba(MgAs)2 by Materials Project

Ba(MgAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent As3- atoms to form BaAs6 octahedra that share corners with twelve equivalent MgAs4 tetrahedra, edges with six equivalent BaAs6 octahedra, and edges with six equivalent MgAs4 tetrahedra. All Ba–As bond lengths are 3.37 Å. Mg2+ is bonded to four equivalent As3- atoms to form MgAs4 tetrahedra that share corners with six equivalent BaAs6 octahedra, corners with six equivalent MgAs4 tetrahedra, edges with three equivalent BaAs6 octahedra, and edges with three equivalent MgAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–51°. All Mg–As bond lengths are 2.73 Å. As3- is bonded in a 7-coordinate geometry to three equivalent Ba2+ and four equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(MgAs)2 by Materials Project

Ca(MgAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent As3- atoms to form CaAs6 octahedra that share corners with twelve equivalent MgAs4 tetrahedra, edges with six equivalent CaAs6 octahedra, and edges with six equivalent MgAs4 tetrahedra. All Ca–As bond lengths are 3.09 Å. Mg2+ is bonded to four equivalent As3- atoms to form MgAs4 tetrahedra that share corners with six equivalent CaAs6 octahedra, corners with six equivalent MgAs4 tetrahedra, edges with three equivalent CaAs6 octahedra, and edges with three equivalent MgAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 17–55°. There are three shorter (2.66 Å) and one longer (2.75 Å) Mg–As bond lengths. As3- is bonded to three equivalent Ca2+ and four equivalent Mg2+ atoms to form a mixture of distorted edge and corner-sharing AsCa3Mg4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAs by Materials Project

MgAs is Modderite-like structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six equivalent As2- atoms. All Mg–As bond lengths are 2.80 Å. As2- is bonded in a 6-coordinate geometry to six equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(MgAs)2 by Materials Project

Eu(MgAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg2+ is bonded to four equivalent As3- atoms to form MgAs4 tetrahedra that share corners with six equivalent EuAs6 octahedra, corners with six equivalent MgAs4 tetrahedra, edges with three equivalent EuAs6 octahedra, and edges with three equivalent MgAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–54°. There are three shorter (2.68 Å) and one longer (2.74 Å) Mg–As bond lengths. Eu2+ is bonded to six equivalent As3- atoms to form EuAs6 octahedra that share corners with twelve equivalent MgAs4 tetrahedra, edges with six equivalent EuAs6 octahedra, and edges with six equivalent MgAs4 tetrahedra. All Eu–As bond lengths are 3.17 Å. As3- is bonded to four equivalent Mg2+ and three equivalent Eu2+ atoms to form a mixture of distorted corner and edge-sharing AsEu3Mg4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Spatially resolved molecular gas properties of host galaxy of Type I superluminous supernova SN 2017egm

Abstract We present the results of CO(1–0) observations of the host galaxy of a Type I superluminous supernova (SLSN-I), SN 2017egm, one of the closest SLSNe-I at z = 0.03063, by using the Atacama Large Millimeter/submillimeter Array. The molecular gas mass of the host galaxy is Mgas = (4.8 ± 0.3) × 109 M⊙, placing it on the sequence of normal star-forming galaxies in an Mgas–star-formation rate (SFR) plane. The molecular hydrogen column density at the location of SN 2017egm is higher than that of the Type II SN PTF10bgl, which is also located in the same host galaxy, and those of other Type II and Ia SNe located in different galaxies, suggesting that SLSNe-I have a preference for a dense molecular gas environment. On the other hand, the column density at the location of SN 2017egm is comparable to those of Type Ibc SNe. The surface densities of molecular gas and the SFR at the location of SN 2017egm are consistent with those of spatially resolved local star-forming galaxies and follow the Schmidt–Kennicutt relation. These facts suggest that SLSNe-I can occur in environments with the same star-formation mechanism as in normal star-forming galaxies.

Hatsukade, Bunyo (ORCID:0000000164698725)↗
DOE OSTI2021

Redshift evolution of the H2/H i mass ratio in galaxies

ABSTRACT In this paper, we present an attempt to estimate the redshift evolution of the molecular to neutral gas mass ratio within galaxies (at fixed stellar mass). For a sample of five nearby grand design spirals located on the main-sequence (MS) of star-forming galaxies, we exploit maps at 500 pc resolution of stellar mass and star formation rate (M⋆ and SFR). For the same cells, we also have estimates of the neutral (MH i) and molecular ($M_{\rm H_2}$) gas masses. To compute the redshift evolution, we exploit two relations: (i) one between the molecular-to-neutral mass ratio and the total gas mass (Mgas), whose scatter shows a strong dependence with the distance from the spatially resolved MS, and (ii) the one between $\log (M_{\rm {H_2}}/M_{\star })$ and log (MH i/M⋆). For both methods, we and that $M_{\rm H_2}$/MH i within the optical radius slightly decreases with redshift, contrary to common expectations of galaxies becoming progressively more dominated by molecular hydrogen at high redshifts. We discuss possible implications of this trend on our understanding of the internal working of high-redshift galaxies.

Morselli, Laura (ORCID:0000000307532571)↗